The present invention relates generally to an expansion joint used to couple electrical conduits. More particularly, the present invention relates to an expansion joint coupling which is attachable to conduits without disassembly, and which maintains ground continuity thereacross upon expansion of the joint.
Electrical conduit is typically used to support runs of electrical wiring. These conduits may be metallic, and in certain instances are required to be grounded. Conduits supporting such electrical wiring may be interconnected at electrical fitting joints. Certain of these joints provide for thermal expansion, permitting relative movement between the conduits in response to ambient temperature fluctuations. These joints must not only provide for relative movement between the conduits, but also must maintain ground continuity across the conduits during such movement.
It is well known to use expansion joints to effect connection between conduits. Certain existing expansion fittings use an external bonding jumper to provide ground continuity. This method requires additional ground clamps and straps to be installed to one end of the conduit and then connect to the other conduit end in similar manner. Installation requires disassembly of the expansion coupling, insertion of the conduit through the hub nut, screw attachment of the bushing to the conduit, insertion of sub-assembly into the body of the expansion joint and tightening of the hub nut to the required torque value. This requires more time to install (more labor hours), and requires an additional component such as external bonding jumpers to be purchased and installed.
Other expansion fittings include a ring shaped grounding element that is mounted on a screw threaded bushing formed in a movable end portion where one end of the conduit is threaded. This bushing with the ring shaped grounding element is disposed in a sliding connection with the inner cylindrical surface of the coupling body. The other conduit end is threaded into the coupling body""s reducer hub end. While this expansion coupling does not require an external bonding jumper, it still requires disassembly during installation. Another disadvantage is the required extra effort to insert the screw thread bushing with the ring shaped grounding element into the inside diameter of the expansion coupling body.
Examples of expansion joints are shown in U.S. Pat. Nos.: 3,783,178; 4,250,350; 4,558,173; and 5,466,890. Each of these expansion joints requires, to some extent, disassembly of components of the expansion joint in order to attach the conduits to the joint. Even partial disassembly of the expansion joint is difficult and time consuming to perform in the field. Much of the disassembly of the expansion joint is necessitated by the fact that most of the expansion joints of the prior art require that one of the conduits be attached to the ground mechanism which maintains ground continuity between the conduit and the joint during relative movement therebetween. Thus, while one conduit may be easily fixably attached to one end of the joint, the other conduit must be attached to the ground components of the joint which are designed to be movably positioned within the joint itself.
It is desirable, therefore, to provide an expansion joint which allows a direct attachment of conduits to the ends thereof, yet maintains ground connection across the conduits during relative movement therebetween.
The present invention provides an expansion joint that allows direct attachment of conduits to the ends thereof without the need for disassembling the expansion joint. The expansion joint includes a first expansion joint body which is elongate and is attachable at one end directly to an electrical conduit. The first joint body movably accommodates therein a second joint body, which is attachable at one end to an electrical conduit. Grounding means is provided between the first and second joint bodies, which maintains ground continuity between the joint bodies upon relative movement therebetween.
The present invention further provides an electrical expansion joint for interconnecting a pair of electrical conduits comprising an elongate generally cylindrical outer body having an attachment end for attachment to one of the conduits and a reception end for receiving the other conduit. A conduit mounting member is movably supported within the outer body in ground continuity therewith. The conduit mounting member is attachable to the other conduit while the conduit mounting member is movably supported within the outer body.
In an embodiment of the present invention, there is provided an electrical expansion joint for interconnecting first and second electrical conduits including an elongate generally cylindrical outer body having an attachment end for attachment to the first electrical conduit and an opposed reception end. An elongate generally cylindrical inner body includes an attachment end for attachment to the second electrical conduit and an opposed insertion end for insertion into the reception end of the outer body for relative movement therein. A ground member is interposed between the inner and outer bodies for maintaining ground continuity therebetween throughout the relative movement.